Normally when I read this book to elementary kids I do a color mixing activity. This activity is my favorite to do since the results are like magic as the colors mix. I also like it because it uses simple materials that you probably already have on hand. Also each child can do the color mixing in his or her space and be able to see the results up close and personal. Here is another link to the printables to use with this activity.
So if you are teaching colors in Spanish Pinta Ratones and the above activity are the way to go. Have fun with color!